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Author Topic: cbr600f3 internal into cb1 stanchions  (Read 224 times)
uglygit
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« on: April 10, 2020, 11:55:31 AM »

For anyone looking to fit f3 forks into cb1 legs instead of having 20mm sticking above the handle bar clamps using the f3 legs, I have been out to the shed and took a few measurements,

It would seem that there are three issues with fitting the cbr600f3 internals into cb1 stanchions.

firstly because the stanchions on the cb1 are 20mm shorter when the cbr cartridge is fully compressed and the preload set to the first/stiffest notch the damper unit will protrude past the end of the standard cb1 stanchion by about 9mm (3mm or so sits in a recess in the slider) the protrusion would allow the valve stacks to come into contact before the fork is fully compressed/bottomed in the slider.

To stop the damper unit bottoming out and limiting wheel travel you would ideally shorten the internals (damper needle and rod) by 20mm to bring everything back into position and cut 20mm off the spring spacer to correct the preload. The damper lock nut is m10x1.0 thread.

people that do the same f3 swap on sv650 and bandits suffer the same problem because they share the same 613mm fork length as the cb1.

But after a bit of measuring you could probably get away with winding the preload adjuster out and adjusting the length of the internal spacer to compensate, this is because winding the preload adjuster out has the same effect as shortening the damper rod.

setting the preload to notch 5 and cutting the internal spacer down by only 14mm instead of 20 should result in 5-6mm internal clearance and a preload that is the same as the stock 3 notch setting, just remember to never wind the preload adjuster down past the third notch or you risk bottoming out again.

Secondly, because the CBR cartridge is a larger diameter they do not fit past the lower shuttles of the cb1 fork, you need to either

grind the end of the stanchion so that you can remove the shuttles from the CBR fork and install them into the cb1 stanchions, you will need a welder to do this also you need to drill 2 new 6mm oil holes 35mm further up the tube 180 to reach other.

Or you can modify the cb1 shuttles by removing the nylon flow restrictor and spring clip then grind a few mm from the four protrusions on the top out spring seat to allow the cartridge to pass through, you may still need to drill the extra holes to ensure the original shuttle doesn't effect the damping.


Thirdly (may not actually be an issue)

The f3 damper cartridge has 150mm of travel in total, fully assembled a cb1 fork measures 120mm from the end of the stanchion to the top of the damper rod cap, with shortened f3 internals the damper measures 125mm, the extra 5mm length shouldn't cause any functional issues it just means you need to add 5mm to your sag settings.

but if you do want to correct it you will need to fit a 5mm spacer between the top out spring and the stanchion.

for those that cut the internals there should clearance internally to take the spacer without limiting travel, you will just need to cut an extra 5mm off the preload adjuster.

for those that didn't shorten the f3 internals you will have to wind the preload adjuster fully out (notch 7) to compensate for a 5mm top out spacer, and you will not be able to go past notch 5 without risking losing travel/ bottoming on the dampers.

If you don't shorten the preload spacer the additional 5mm to compensate for the top out spacer would be the equivalent of having two extra notches of preload wound in.
.

« Last Edit: April 11, 2020, 11:39:56 AM by uglygit » Logged

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eyhonda
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« Reply #1 on: April 26, 2020, 08:09:59 AM »

Good info!  Thank you!
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